In the field of producing petroleum coke in an oil refinery, a process called delayed coking is in common and growing use. Heavy residual oil from the bottom of the fractionate column is heated to about 950 degrees F, some chemicals are added, and the fluid is pumped into a large alloy steel drum. The drum is commonly 25 to 27 feet in diameter and two to three times as tall. The liquid turns into hard coke inside the drum, when it becomes stagnant, by the hydrocarbon cracking process, releasing light hydrocarbon products and leaving coke as the low grade residual product in the drum. To remove the hard coke, it must be cut out of the drum with high pressure water, cutting the hard coke into pieces that can fall out the bottom of the drum.
To cut coke out of a drum that is full, a three foot flange is removed from the top of the drum and a six foot flange is removed from the bottom of the drum. A rotating combination drill bit and cutting head about 18" diameter is mounted on the lower end of a long hollow drill rod about 6" in diameter, and the drill bit is then lowered into the drum, on the drill stem, through the three foot flange opening at the top. A hole about 18" in diameter is drilled down through the entire vertical height of the coke in the drum, the drill bit coming out through the bottom of the hard coke mass. Then the rotating drill is raised back up a short distance into the hard coke mass, and high pressure water at about 2500 psi and more is pumped down the hollow drill rod, and out a group of positioned jet nozzles in the sides of the cutting head part of the drill bit. The nozzles shoot jets of water horizontally outwards, rotating slowly with the drill rod, and those jets cut the coke into pieces, which fall out the open bottom of the drum, into a pit. The drill is raised slowly up from the bottom the entire vertical height of the coke mass, cutting the coke out of the drum all the way up to the top, the coke falling out the six foot opening at the bottom of the drum. The drill rod is then withdrawn out the three foot flange opening at the top of the drum. The six foot flange at the bottom of the drum is then bolted back in place, along with the three foot flange at the top of the drum. The drum is then clean and ready for the next filling cycle with the heavy residual oil.
The process of removing and replacing the removable six foot flange or cover is called heading and unheading. The removable flange or cover is manually bolted on and unbolted from a stationary complimentary six foot flange at the bottom of the vessel, using air wrenches, on over seventy large nuts. It is dangerous work, with several risks associated with the procedures. There have been fatalities, and many burns suffered, and there is significant physical trauma associated with the manual work.
So unpleasant is the above-described work of unheading and heading of the six foot flange, it is frequently subcontracted by the refineries to outside contractors, who employ workers specialized in this difficult work. Other refineries have their own employees perform the work, but they rotate the workers frequently to other tasks, so as to minimize the effects of the harmful trauma.
For the above reasons, the oil refineries with delayed coker process units universally desire to automate the unheading procedure, to minimize the strenuous manual work and risk of accidents therefrom.
There are currently two known devices on the market to facilitate heading and unheading. One, a clam shell type of hinged bottom cover, swings down and away under hydraulic power, opening the bottom of the drum for the coke to drop out. It is very big and heavy, requires much structural support to be added to existing drums at considerable expense, and in many cases is even impossible to implement because of limited strength of the existing drums. Of great importance is the difficulty in this design to develop the required large force, typically about 1,000,000 pounds, required to hold the bottom flange to the bottom of the drum with sufficient force to develop the needed gasket squeeze. It has received very little acceptance. The other device has been sold in many refineries, and is the device of choice at present. It has a flange that is held up against the bottom of the vessel with tensioned bolts. Instead of tensioning them with a threaded nut, as in a bolt on the manually installed flanges, the bolts are tensioned by stretching them with an inflatable hollow ring of gas-filled metal. Then a mechanical locking ring is positioned so that the tension is maintained by the mechanical locks being put into place. The device is complicated, with several hundred moving parts, and is quite expensive, about $1,000,000 each. It also is very expensive to install, and takes a long time to complete all the work, at great cost in lost production. While new drums can be designed to use the device, it is difficult to add to existing installations.
The invention relates to an alternative device (and method) for removing and replacing flanges, particularly six foot flanges, for coke drums and the like, that is simple, compact, quick and easy to install, uses existing technology, is less expensive than prior art alternatives discussed above, and is particularly well suited to being retrofitted to existing drums (as well as usable in new installations). The invention seeks to make the heading and unheading of delayed coker drums safer for personnel to perform, by removing the source of severe work-related trauma to personnel. This is accomplished through a novel means of automated clamping of the removable six foot flange firmly to the stationary flange at the bottom of the drum. The invention also speeds up the procedure so that the cycle time for the process can be reduced, without compromise in safety or human effort. The invention also renders the addition of this new closure device onto the hundreds of existing coker drums to a simple, quick, and inexpensive procedure, as compared to the difficult, expensive, and time consuming requirement of the inflatable hollow ring device of the prior art described above. The invention dramatically increases the closure integrity, and therefore the safety, of the large gasket for the six foot flange; and the invention provides a mechanism that can be cleared easily, with an air hose or steam jet just before heading, of any fallen coke accumulations that commonly foul mechanisms of the prior art.
The invention relates to a method and apparatus for semi-automatically clamping and unclamping distinct elements together so as to effect ready removal of a closure for a drum, in place of the removable flange or closure described above, and without the drawbacks discussed above. In the preferred embodiment three or four clamping ring sectors are provided associated with a spool piece (adaptor) and revised closure flange which takes the place of the prior art removable closure flange, the spool piece bolted to the stationary drum flange and the revised closure flange being capable of being made from the prior art closure flange in existing installations. However two clamping ring sectors might be used in some installations, or more than three or four (e. g. 6-8). Powered devices, which may be controlled automatically or semi-automatically, move the clamping ring sections between a position in which they clamp the revised closure flange in place to the spool piece portion of the stationary flange on the drum, and a position in which they release the revised closure flange. The powered devices may comprise any powered actuators, including motors, solenoids, or the like, but preferably comprises linear actuators such as hydraulic or pneumatic cylinders with reciprocating piston rods. Other actuators, which also may include motors, solenoids, or the like, but preferably comprise linear actuators such as hydraulic or pneumatic cylinders with reciprocating piston rods, may be mounted on the drum or other stationary location to move the clamping ring sectors out of the way when clamping action is released, so that the revised closure flange may be supported by conventional existing vertically movable supports (e. g. fluidic cylinders). The method of the invention typically requires human intervention only to remove a small number of easily removed jamming pins, and to actuate the powered devices, all of which can be done safely and without significant or dangerous physical effort. The drum cleaning procedure may then be performed just as in the prior art procedure described above.
According to one aspect of the present invention, there is provided method of modifying an existing substantially vertical coke drum to semi-automate heading and unheading, the coke drum having a bottom stationary flange having a plurality of substantially vertical openings through which bolts pass, and a bottom removable flange at least forty inches in diameter and having a plurality of substantially vertical openings therein to receive the bolts which pass through the stationary flange openings and having a conduit through which hydrocarbon fluids pass during coke production, the method utilizing a spool piece having a generally upwardly facing annular tapered clamping surface, a plurality of clamp ring sectors each having spaced first locking surfaces and generally downwardly and upwardly annular sector tapered clamping surfaces, a plurality of second locking surfaces; a plurality of first powered actuators for moving the second locking surfaces, and a plurality of second powered actuators for moving the clamp ring sectors. The method comprises the steps of: (a) detaching the bottom removable flange and hydrocarbon fluid conduit from the coke drum bottom stationary flange; (b) forming a generally downwardly facing annular tapered clamping surface on the bottom removable flange, to produce a revised removable flange, or replacing the bottom removable flange with a new flange having a generally downwardly facing annular tapered clamping surface, and a hydrocarbon fluid conduit; (c) attaching the spool piece to the drum stationary flange; (d) attaching the plurality of second actuators to the drum; (e) moving the revised or new movable flange into sealing engagement with the spool piece; (f) using the second powered actuators, moving the tapered clamping surfaces of the clamp ring sectors into contact with the tapered clamping surfaces of the spool piece and the revised or new removable flange; and (g) using the first powered actuators, moving the first locking surfaces into locking engagement with the second locking surfaces.
The tapered annular clamping surfaces of the revised or new bottom flange and spool piece may have a first radius of curvature, and the clamp ring sectors tapered annular sector clamping surfaces may have a second radius of curvature, approximately 2-13% greater than the first radius; and wherein step (f) may be practiced so as to cause a center portion only of each clamp ring sector tapered annular sector to contact the spool piece and revised or new bottom flange tapered annular clamping surfaces; and wherein step (g) may be practiced to cause the clamp ring sectors to bend to cause end portions thereof to come into contact with the spool piece and revised or new bottom flange tapered annular clamping surfaces and provide the desired effective clamping force at the center portion.
Step (c) may be practiced by connecting the bolts from the drum flange to the spool piece using nuts. There may also be the further steps of (h) unheading the drum by first moving the first powered actuators to move the first and second locking surfaces out of locking engagement with each other, and then (i) using the second powered actuators, moving the ring clamp sectors away from the drum while the revised or new bottom flange is supported by an external support, so that the bottom flange is free to move away from the drum upon movement of the external support.
There may also be the further steps of (j) moving the bottom flange away from the drum so that an opening at least 30 inches (preferably at least 40 inches, more desirably at least 60 inches, most desirably about 72 inches) in diameter is provided in the bottom of the drum, (k) removing coke from the drum through the bottom opening (using the conventional techniques described above); and (l) repeating steps (e)-(g) to move and seal the bottom flange back into a position covering the opening in the bottom of the drum.
Typically, the first actuators comprise linear actuators connected to the first locking surfaces by a linkage, and each of the linkages is connected to a ring clamp sector using a removable jamming pin; and comprising the further step (j), before step (i), of removing the jamming pins.
According to another aspect of the present invention a coke drum assembly is provided comprising the following components: A substantially vertical coke drum having a top with a removable top flange, a bottom with a stationary first sealing structure, and a movable second sealing structure (e. g. a removable bottom flange with a hydrocarbon fluid conduit therein) larger than the removable top flange that is adapted to be moved from a first position sealingly connected to the first sealing structure, and a second position detached from the first sealing structure. The first and second sealing structures having, respectively, first and a second tapered annular clamping surfaces. A plurality (preferably 3 or 4, although 2, or 5-8, may be provided) of clamp ring sectors, each sector having third and fourth tapered annular sector clamping surfaces for respectively engaging the first and second tapered annular clamping surfaces. A plurality of first locking structures each having first locking surfaces. Second locking surfaces formed in each of the clamp ring sectors, the second locking surfaces for cooperation with the first locking surfaces to hold the clamp ring sectors to each other so that the clamp ring sectors hold the second sealing structure with respect to the first sealing structure in the first position. A plurality of first powered actuators mounted to the ring sectors and the first locking structure for moving the first locking structures with respect to the second locking surfaces between a first position in which the clamp ring sectors are clamped together, and a second position in which the clamp ring sectors are movable apart from each other; and a plurality of second powered actuators distinct from the first actuators and connected to the clamp ring sectors to move the clamp ring sectors away from the first and second sealing structures when the first locking structure is in the second position. The stationary first sealing structure may comprise a bottom flange of the drum, and a spool piece extending downwardly from the bottom flange; and wherein the movable second sealing structure comprises a movable flange. Each of the first powered actuators preferably comprises a linear actuator, and each of the plurality of second actuators comprises a linear actuator operatively connected adjacent one end thereof to the drum and is adjacent another end thereof to a the clamp ring sector. For example, each of the first powered linear actuators is connected to the first locking structure by a linkage, and the linkage is releasably connected to a the clamp ring section by a removable jam pin.
Preferably the first locking surfaces are male surfaces, and the second locking surfaces are female, although they may be switched, or mixed. To enhance clamping efficiency while minimizing the number of clamp ring sectors, preferably the first and second tapered annular clamping surfaces have a first radius of curvature, and the clamp ring sectors tapered annular sector clamping surfaces having a second radius of curvature, approximately 2-13%, preferably 5-10%, greater than the first radius so as to cause only a center portion of each clamp ring sector tapered annular sector to contact the first and second tapered annular clamping surfaces, and to cause the clamp ring sectors to bend to cause end portions thereof to come into contact with the first and second tapered annular clamping surfaces and provide the desired effective clamping force at the center portion.
In one preferred embodiment, each of the first locking structures comprises a relatively stationary locking surface spaced from a relatively movable locking surface, the relatively movable locking surface mounted on a pivotal link operatively connected a one of the first actuators. Also, typically the second movable sealing structure comprises a bottom flange generally circular in dimension and having a diameter of over about five feet [60 inches], typically about 72 inches or even greater in diameter.
The invention is advantageous compared to other known clamping systems. For example the Grayloc.RTM. connector (available from Gray Tool Co. of Harvey, La.) connects a tapered inner surface clamp by bolts to tapered outer surface hubs (or hub pieces), with a distinct, ribbed, metal seal ring between the hubs. Thus operation is not semi-automatic, an extra large component (the ribbed seal ring) is provided, and known maximum size is 30 inch diameter hubs. The invention, on the other hand, uses only a thin, flat, metal gasket recessed in one or more main grooves formed in the spool piece and bottom flange, is used with 72" diameter clamped components, and is semi-automatic (virtually automatic) in operation. The main grooves may include relief grooves connected to a source of steam.
According to another aspect of the invention there is provided a semi-automatic clamping assembly comprising the following components:
A stationary first sealing structure (e. g. a stationary bottom flange of a coke drum, with a spool). A movable second sealing structure (e. g. a bottom removable flange) that is adapted to be moved between a first position sealingly connected to the first sealing structure, and a second position detached from the first sealing structure, the second sealing structure having a diameter of over about thirty inches (preferably over 36 inches, more preferably over 60 inches, e.g. about 72 inches or more). The first and second sealing structures having, respectively, first and second tapered annular clamping surfaces. A plurality of clamp ring sectors, each sector having third and fourth tapered annular sector clamping surfaces for respectively engaging the first and second tapered annular clamping surfaces. A plurality of first locking structures each having first locking surfaces. Second locking surfaces formed in each of the clamp ring sectors, the second locking surfaces for cooperation with the first locking surfaces to hold the clamp ring sectors to each other so that the clamp ring sectors hold the second sealing structure with respect to the first sealing structure in the first position. A plurality of first powered actuators mounted to the ring sectors and the first locking structure for moving the first locking structures with respect to the second locking surfaces between a first position in which the clamp ring sectors are clamped together, and a second position in which the clamp ring sectors are movable apart from each other, and a plurality of second powered actuators distinct from the first actuators and connected to the clamp ring sectors to move the clamp ring sectors away from the first and second sealing structures when the first locking structure is in the second position.
The details of the components are preferably as described above with respect to an earlier aspect of the invention.
According to yet another aspect of the present invention, there is provided an assembly for providing substantially leak-proof sealing of a volume (e.g. a coke drum) in general. The assembly comprises the following components: A volume having fluent material at a first pressure. First and second substantially annular flanges having face-to-face engagement along first and second surfaces thereof, the surfaces abutting the inner volume at a first end portion thereof, and abutting an exterior volume at a second end portion thereof. First and second main substantially annular grooves formed in the first and second surfaces, respectively. A relief groove formed in each of the main grooves. An annular metal gasket disposed in the main grooves, the gasket having a plurality of through extending openings therein extending from one relief groove to the other; and a passage extending through one of the flanges and connected to a source of steam at a second pressure, higher than the first pressure, so that steam is supplied to the relief grooves and if there is leakage between the first and second surfaces it is of steam.
It is the primary object of the present invention to provide for the heading and unheading of coke drums in a semi-automatic safe, easy, and quick manner. This and other objects of the invention will become clear from a detailed description of the invention, and from the appended claims .